1. Field of the Invention
The present invention relates to a lock mechanism for a stage apparatus which locks a movable stage of the stage apparatus in a non-operational state when the movable stage, which is freely movable along a specific plane, is in a non-operational state.
2. Description of the Prior Art
An example of a movable stage which is movable in a specific X-direction and a Y-direction orthogonal to the X-direction, and to which an image pickup device is fixed on a front surface thereof, is disclosed in Japanese Patent No. 3431020. The lock mechanism disclosed therein is provided with one cylindrical boss projecting from the back surface of a movable stage, and first and second abutting members provided behind the movable stage on mutually opposing sides of the cylindrical boss. The first and second abutting members are movable in a direction parallel to the movable stage.
When the movable stage is in a non-operational state where no hand-shake correction is performed, the first abutting member and the second abutting member mutually move toward a locked position. Accordingly, since approximately half-circle shaped engaging recesses, respectively formed on opposing surfaces of the first and second abutting members, clasp the cylindrical boss, the movable stage is locked by the first and second abutting members.
Since the above described lock mechanism is a construction whereby one cylindrical boss is clasped by the approximately half-circle shaped engaging recesses of the first and second abutting members, the movable stage cannot be securely locked without the first and second abutting members contacting the cylindrical boss with a strong force.
However, in order for the first and second abutting members to contact the cylindrical boss with a strong force, the size of the driving device of the lock mechanism needs to be increased, which undesirably increases the size of the lock mechanism and the stage apparatus.
Furthermore, in the case where this lock mechanism of the prior art is applied to a camera-shake (hand-shake) correction apparatus which corrects ‘rotational shake’, an additional problem occurs. Namely, in this kind of camera-shake correction apparatus, the stage is rotatable. However, in the above described lock mechanism of the prior art, since there is only one boss (i.e., the cylindrical boss), even if the first and second abutting members clasp this boss, the movable stage cannot be locked so as to be prevented from being rotated.